1. Field of Invention
This invention is directed to systems and methods for authenticating documents.
2. Description of Related Art
A receiver of a document often wants to ensure that the document is an unchanged original from a sender. Thus, senders have endeavored to add security measures to their documents so that a receiver can verify that the document is genuine.
One security measure that is employed is outlined in the commonly owned U.S. patent application Ser. No. 09/346,559 filed on Jun. 30, 1999, (hereinafter the '559 application), which is incorporated herein by reference in its entirety. The '559 application discloses methods of compressing an original document image, digitally signing the compressed image data and writing the signed compressed image data onto unused space of the document. The receiver/verifier then receives the document, including the signed compressed image data. The verifier generates a verifying image from the signed compressed image data and compares the verifying image to the original document to ensure that the document has not been altered.